Paper Comprising Fiber of Citrus Peel

ABSTRACT

A paper containing citrus peel fiber contains 20 to 60 weight parts of citrus peel fiber with respect to 100 weight parts of paper mulberry fiber. The citrus peel fiber is a peel fiber of one selected from the group consisting of mandarin orange, lemon, orange, Kiyomi and Dekopon. The paper containing citrus peel fiber is excellent in tensile strength, tear strength, bursting strength and folding endurance, and has superior preservability with pH close to neutrality. The paper containing citrus peel fiber of the invention also has a yellowish and/or reddish aesthetic color, excellent tactile sensation and high vapor transmission, and thus is adequate to be used as high grade wall paper and window paper. Furthermore, since the paper containing citrus peel fiber of the invention is manufactured by using by-products created in the course of processing citruses, it is possible to reduce manufacturing costs as well as decrease waste, thereby preventing pollution.

TECHNICAL FIELD

The present invention relates to a paper containing citrus peel fiber, and more particularly, to a paper containing peel fiber of a citrus such as mandarin orange, lemons, orange, Kiyomi and Dekopon (Shiranuhi) together with mulberry fiber.

BACKGROUND ART

Traditional Korean paper, also referred to as “Hanji,” is manufactured by processing bast fiber, which is obtained from peels of paper mulberry trees or mulberry trees, and has high texture strength and excellent fibrous connection since the length of the fiber is significantly longer than those of common pulps. Common paper is hydrolyzed as time passes due to its strong acidity of about pH 4 to pH 5.5, and thus becomes less conservable. However, Korean paper has a long lifetime and remains highly hygroscopic (i.e., has high vapor transmission). In addition, Korean paper is evaluated as a high grade paper due to texture properties with natural beauty. However, the usage of Korean paper is gradually decreasing, and to date, being applied to restricted fields such as industrial arts and interiors. Thus, Korean paper merely keeps itself in existence. In order to widen the usage, various types of Korean paper are consistently introduced, which include functional Korean paper where oak charcoal, lacquer poison and the like are added.

In the meantime, a massive amount of citrus peels are produced in the course of processing citruses in Jeju, Korea. A portion of the citrus peels are utilized as feeds and herb medicines, but a majority of the citrus peels are discarded. Sometimes, the citrus peels are even thrown away illegally. Thus, it is necessary to devise an approach which can utilize the citrus peels as resources in order to prevent land and marine pollution and newly create added values.

Prior to the present invention, the inventor previously filed Korean Patent Application No. 10-2006-0004265, titled “Korean Paper Made of Citrus Peel.” In this document, the inventor proposed a Korean paper manufacturing process using the citrus peels where pulverized citrus peel powder is added in a beating procedure. Korean paper manufactured using the citrus peels assumes unique color and fragrance of citruses while maintaining the quality of common Korean paper.

However, the citrus peel power does not have excellent fibrous connection with mulberry fiber, and thus Korean paper containing the citrus peels are thicker and more bulky but have a lower density with respect to common Korean paper manufactured by inputting an adhesive material in the same amount. In addition, Korean paper containing the citrus peels also have relatively lower tensile strength, bursting strength, tear strength and folding endurance.

DISCLOSURE Technical Problem

Accordingly, the present invention has been made to solve the above-mentioned problems occurring in the prior art, and an object of the present invention is to manufacture high grade paper, which is excellent in strength, vapor transmission and preservability, and have aesthetic colorful patterns, by using fiber produced from citrus peels as raw materials of the paper. Another object of the invention is to utilize waste outputted in the course of processing citruses as resources in order to reduce manufacturing costs while preventing pollution.

Technical Solution

The present invention relates to a paper containing peel fiber of a citrus such as mandarin orange, lemon, orange, Kiyomi and Dekopon (Shiranuhi) together with mulberry fiber.

In the present invention, the terminology “citrus” collectively refers to mandarin orange, lemon, orange, Kiyomi, Dekopon and so on. The terminology “citrus peel fiber” collectively refers to fibers prepared by cooking peels of citruses such as mandarin orange, lemon, orange, Kiyomi and Dekopon in a sodium hydroxide solution to remove cellulose oil therefrom, cleaning the cooked citrus peels, and beating the cleaned citrus peels together with water in a beater.

In the present invention, mulberry fiber is prepared by impregnating, cooking and beating mulberry wood according to the same process as for common Korean paper.

An adhesive may be added to disperse fiber and prevent entanglement, thereby facilitating paper forming, making basis weight uniform, and enhancing paper strength. Examples of the adhesive may include polyethylene oxide (PEO), polyamide and so on.

The paper containing citrus peel fiber of the invention is manufactured by mixing an adhesive into 100 weight parts of paper mulberry fiber and 20 to 60 weight parts of citrus peel fiber, the paper mulberry fiber prepared by beating mulberry wood, the citrus peel fiber prepared from peels of citruses such as mandarin orange, lemon, orange, Kiyomi and Dekopon; and forming the mixture into paper, and compressing and drying the paper.

ADVANTAGEOUS EFFECTS

The paper containing citrus peel fiber of the invention is excellent in tensile strength, tear strength, bursting strength and folding endurance, and has superior preservability with pH close to neutrality. The paper containing citrus peel fiber of the invention also has a yellowish and/or reddish aesthetic color, excellent tactile sensation and high vapor transmission, and thus is adequate to be used as high grade wall paper and window paper. Furthermore, since the paper containing citrus peel fiber of the invention is manufactured by using by-products created in the course of processing citruses, it is possible to reduce manufacturing costs as well as decrease waste, thereby preventing pollution.

DESCRIPTION OF DRAWINGS

FIG. 1 is a sectional view illustrating a vapor transmission cup prepared for vapor transmission test; and

FIG. 2 is pictures illustrating the surface of paper manufactured according to Examples 1 to 12, taken with an imaging device.

MODE FOR INVENTION Example 1 Manufacturing of Mandarin Peel Paper 1

200 g of dried mandarin orange peels (also referred to as “mandarin peels”) were placed into a 5% sodium hydroxide solution, and cooked at 100° C. for 30 minutes to soak out cellulose oil. The cooked peels were cleaned with water three times, placed into a Holland beater together with 1.8 kg of water, and beaten for 20 minutes, thereby producing fiber of mandarin peel or mandarin peel fiber.

10 kg of mulberry fiber (90 wt % moisture) prepared by cooking mulberry wood, 2 kg of the mandarin peel fiber prepared as above and 45 g of PEO were mixed and stirred. The stirred mixture was placed into a paper-making tank and formed into a sheet of paper by a twin-wire sheet former. The paper was dewatered and compressed in a dehydrator to have a uniform basis weight. The compressed and half-dried paper (40 wt % moisture) was swept with a drying brush, attached in a stack-by-stack manner, and dried in a hot plate dryer, thereby producing Mandarin peel paper 1.

Example 2 Manufacturing of Mandarin Peel Paper 2

Mandarin peel paper 2 was manufactured in the same process as in Example 1 except that 10 kg of the mulberry fiber prepared by beating mulberry wood, 4 kg of the mandarin peel fiber and 45 g of PEO were mixed.

Example 3 Manufacturing of Lemon Peel Paper 1

Lemon peel paper 1 was manufactured in the same process as in Example 1 except that mandarin oranges were substituted by lemons.

Example 4 Manufacturing of Lemon Peel Paper 2

Lemon peel paper 2 was manufactured in the same process as in Example 2 except that mandarin oranges were substituted by lemons.

Example 5 Manufacturing of Lemon Peel Paper 3

Lemon peel paper 3 was manufactured in the same process as in Example 4 except that 10 kg of the mulberry fiber prepared by beating mulberry wood, 6 kg of the mandarin peel fiber and 45 g of PEO were mixed together.

Example 6 Manufacturing of Orange Peel Paper 1

Orange peel paper 1 was manufactured in the same process as in Example except that mandarin oranges were substituted by oranges.

Example 7 Manufacturing of Orange Peel Paper 2

Orange peel paper 2 was manufactured in the same process as in Example 2 except that mandarin oranges were substituted by oranges.

Example 8 Manufacturing of Kiyomi Peel Paper 1

Kiyomi peel paper 1 was manufactured in the same process as in Example 1 except that mandarin oranges were substituted by Kiyomis.

Example 9 Manufacturing of Kiyomi Peel Paper 2

Kiyomi peel paper 2 was manufactured in the same process as in Example 2 except that mandarin oranges were substituted by Kiyomis.

Example 10 Manufacturing of Dekopon Peel Paper 1

Dekopon peel paper 1 was manufactured in the same process as in Example 1 except that mandarin oranges were substituted by Dekopons.

Example 11 Manufacturing of Dekopon Peel Paper 2

Dekopon peel paper 2 was manufactured in the same process as in Example 2 except that mandarin oranges were substituted by Dekopons.

Example 12 Manufacturing of Common Korean Paper

Mulberry fiber prepared by cooking mulberry wood was formed into a sheet of paper by a twin-wire sheet former in a paper-making tank. The paper was dewatered and compressed in a dehydrator to have a uniform basis weight. The compressed and half-dried paper (40 wt % moisture) was swept with a drying brush, attached in a stack-by-stack manner, and dried in a hot plate dryer, thereby producing common Korean paper.

Papercontaining citrus peel fiber of the invention manufactured according to Examples 1 to 11 had an aesthetic pattern with a yellowish or reddish color, which is not observed in common Korean paper, and gave excellent tactile sensation. The following experiments were carried out to test physical properties of the citrus peel paper according to Examples 1 to 11.

Experiment 1 Measurement of Physical Properties of Paper

Specimens of the respective paper manufactured according to Examples 1 to 12 were extracted according to TAPPI standard test T400, and humidified for 24 hours according to T402 om-83 in a constant temperature and humidity chamber having a temperature 20±1° C. and a relative humidity 65±5%. Then, tests were carried out to measure the physical properties of the paper such as basis weight (oven drying method), thickness, tensile strength, bursting strength, tear strength and folding endurance. The physical properties of the paper were measured according to the test methods reported in Table 1 below, using devices reported in Table 2 below, and the results are reported in Tables 3 and 4 below.

TABLE 1 Item Method Thickness and density TAPPI Standard T200 om-83 Tensile strength TAPPI Standard T494 om-81 Bursting strength TAPPI Standard T403 om-85 Tear strength TAPPI Standard T414 om-82 Folding endurance TAPPI Standard T511 om-83

TABLE 2 Item Device Thickness Model 49-70, Tester Machines INC. Tensile strength Instrun Mini 44, Instron Corporation, USA Tear strength Thwing-Albert Instrument Co., USA Bursting strength Daeil-Machinery Co., Korea Folding endurance Tester Sangyo Co. LTD, Japan

Experiment 2 Measurement of Optical Properties of Paper

Specimens of the respective paper manufactured according to Examples 1 to 11 were extracted according to TAPPI standard test T400, and humidified for 24 hours according to T402 om-83 in a constant temperature/humidity room having a temperature 20±1° C. and a relative humidity 65±5%. Then, tests were carried out on the paper specimens to measure their whiteness with a Hunter whiteness analyzer (Model S4-M, Technidyne Corporation New Albany, India. USA) and their chromaticity with a spectrophotometer (NF 333, Nippon Denshoku Ind. Co., LTD). The results are reported in Table 5 below.

Experiment 3 Measurement of pHs of Paper

The paper manufactured according to Examples 1 to 12 was diced into 1 cm×1 cm pieces. 1.0 g of the individual paper pieces were placed into a 200 ml Erlenmeyer flask together with 100 ml of ion exchange water, and hot water extraction was carried out for 2 hours, followed by cooling. The resultant products were measured of pH, and the results are reported in Table 5 below.

Experiment 4 Measurement of Vapor Transmission of Paper

A vapor transmission cup shaped as shown in FIG. 1 was prepared according to KS F 2607 specification, with an opening area 0.005 m² or more, and distilled water was filled in the cup up to a height 2±0.5 cm from the opening. Paper manufactured according to Examples 1 to 12 was placed, respectively, on the opening of the vapor transmission cup, and maintained with a relative humidity 32.8% in a constant temperature and humidity chamber at a temperature 25° C., and the vapor transmissions of the paper were measured. Vapors migrate from inside the vapor transmission cup of a relative humidity 84.3% through the individual paper to the constant temperature and humidity chamber. After two (2) hour passed from the beginning of the test, the weight of the vapor transmission cup was measured for twenty four (24) hours with one (1) hour interval in order to calculate the amount of vapors migrated. The results are reported in Table 6 below.

Experiment 5 Surface Analysis of Paper

The paper manufactured according to Examples 1 to 12 was diced into 1 cm×1 cm pieces. The paper pieces were photographed by an imaging device (Kenko KCM-Z3, Japan), at a magnifying power 200× and a luminance 5000 Lux, and the photographed images were analyzed by an image analysis program (BMI plus, BumMi Universe Co., LTD., USA). The results are shown in FIG. 2.

TABLE 3 Basis weight Thickness Density Volume Paper type (g/m²) (μm) (g/cm³) (cm³/g) Mandarin peel 1 23.6 84.8 0.28 3.59 Mandarin peel 2 27.8 89.2 0.31 3.21 Lemon peel 1 22.2 92.8 0.24 4.18 Lemon peel 2 21.7 90.3 0.24 4.16 Lemon peel 3 20.1 85.5 0.24 4.25 Orange peel 1 23.0 88.5 0.26 3.84 Orange peel 2 25.2 95.6 0.26 3.79 Kiyomi peel 1 23.5 85.5 0.27 3.64 Kiyomi peel 2 24.6 93.5 0.26 3.80 Dekopon peel 1 29.8 98.8 0.30 3.32 Dekopon peel 2 23.2 85.2 0.27 3.67 Common Korean 25.6 76.3 0.34 2.98 paper

According to the results reported in Table 3 above, it is found that those paper containing citrus peel fiber decreased in density with respect to common Korean paper. It is believed that spaces occupied by citrus peels make fibrous connections rather sparse but increase the volume. The paper containing mandarin peels and Dekopon peels showed a relatively higher density, which is similar to that of common Korean paper. The paper containing lemon peels, however, showed lowest density.

TABLE 4 breaking elongation Tear Folding length rate Bursting strength endurance (km) (%) strength (mNm²/g) (times) Paper Type A B A B (kPam²/g) A B A B Mandarin peel 1 4.7 4.7 8.2 8.5 5.4 49.0 42.1 246 6 Mandarin peel 2 4.0 3.9 5.3 6.1 5.3 43.8 32.6 344 16 Lemon peel 1 7.2 2.9 3.5 6.6 5.4 50.4 41.7 50 1 Lemon peel 2 6.5 4.8 4.2 5.9 5.3 50.3 41.1 53 1 Lemon peel 3 0.7 0.2 3.4 4.2 4.4 39.4 37.3 6 1 Orange peel 1 13.6 11.6 5.4 6.0 6.4 78.1 53.6 496 17 Orange peel 2 11.8 4.32 4.6 6.6 5.8 51.9 44.5 877 16 Kiyomi peel 1 9.2 6.2 2.2 2.9 5.0 43.9 32.4 252 6 Kiyomi peel 2 5.2 5.2 3.7 3.7 4.8 43.9 37.6 322 33 Dekopon peel 1 10.9 4.5 5.6 7.2 5.6 46.0 45.0 164 34 Dekopon peel 2 13.3 4.0 3.4 5.1 5.5 48.9 38.2 97 30 Common Korean paper 8.9 3.0 7.0 10.2 6.5 57.9 41.1 235 13 Note; A: Lengthwise direction B: Lateral direction

According to the results in Table 4 above, the paper containing orange peels, Dekopon peels and Kiyomi peels reportedly increased in tensile strength due to shorter breaking length with respect to common Korean paper. However, except for the paper containing Lemon peel 3, other citrus peel paper generally showed excellent tensile strength: even if the tensile strength was lower than that of Korean paper, the difference was not significant. The extension ratio showed correlation with tensile strength. That is, extension ratio is low at high tensile strength, but high at low tensile strength.

In terms of bursting strength, the citrus peel paper generally showed lower values with respect to common Korean paper, but the difference was not significant. The paper containing Orange peel 1 showed fine bursting strength similar to that of common Korean paper. All of the citrus peel paper showed substantially fine bursting strength.

In terms of tear strength, the paper containing Orange peel 1 showed a higher value over common Korean paper. Although most of the citrus peel containing paper showed tear strength lower than common Korean paper, the difference was not significant. Thus, the citrus peel paper generally was reported with excellent tear strength.

In terms of folding endurance, the paper containing Mandarin peels 1 and 2, Orange peels 1 and 2 and Kiyomi peel 1 showed a higher value over common Korean paper, the paper containing Kiyomi peel 2 showed folding endurance similar to that of common Korean paper, and the paper containing Dekopon peels 1 and 2 and Lemon peels 1 and 2 showed folding endurance lower than that of common Korean paper.

TABLE 5 Whiteness Chromaticity pH (%) L a b Mandarin peel 1 8.25 38.4 80.24 −0.29 14.78 Mandarin peel 2 8.37 37.4 82.85 −0.26 17.41 Lemon peel 1 7.66 46.3 82.08 −0.35 10.86 Lemon peel 2 7.74 42.7 79.98 −0.48 10.84 Lemon peel 3 7.86 30.3 75.36 0.02 14.82 Orange peel 1 8.15 56.3 86.19 −0.10 6.88 Orange peel 2 8.17 39.1 78.83 −0.19 9.62 Kiyomi peel 1 8.32 43.2 82.80 −0.43 12.29 Kiyomi peel 2 7.85 45.0 81.29 0.17 11.58 Dekopon peel 1 8.36 44.8 81.89 0.53 12.63 Dekopon peel 2 8.37 35.7 79.58 −0.01 17.80 Common Korean 7.88 81.5 88.42 −0.61 3.10 paper

In Table 5 above, L=100 indicates white, but L=0 indicates black. A larger +a is more reddish, but a larger −a is more greenish. In addition, a larger +b is more yellowish, but a larger −b is more bluish.

According to the results of Table 5 above, the citrus peel paper had yellowish color and lower whiteness with respect to common Korean paper. The paper containing Kiyomi peel 2 and Dekopon peel 1 were slightly reddish. In terms of pH, most of the citrus peel paper was slightly higher than common Korean paper, but the paper containing the Lemon peels 1 and 2 was slightly lower than common Korean paper. It was judged that the most citrus peel paper has excellent preservability since the pH of the most citrus peel paper was close to neutrality.

TABLE 6 Vapor Vapor Trans- Index of Trans- mission Vapor Vapor mission per area Resistivity Transmission (g/h) (g/m²h) (m²hmmHg/g) (g/m²hmmHg) Mandarin peel 1 0.19894 38.558 0.308 3.247 Mandarin peel 2 0.19528 38.222 0.311 3.215 Lemon peel 1 0.21042 42.084 0.282 3.546 Lemon peel 2 0.20228 40.456 0.294 3.401 Lemon peel 3 0.19099 38.198 0.311 3.215 Orange peel 1 0.20473 40.946 0.290 3.448 Orange peel 2 0.19688 69.376 0.302 3.311 Kiyomi peel 1 0.22947 45.894 0.259 3.861 Kiyomi peel 2 0.20861 41.722 0.285 3.509 Dekopon peel 1 0.19279 38.558 0.308 3.247 Dekopon peel 2 0.19111 38.222 0.311 3.215 Common Korean 0.20007 40.014 0.297 3.367 paper

According to the results of Table 6 above, the paper containing Lemon peels 1 and 2, Orange peels 1 and 3 and Kiyomi peels 1 and 2 had a higher vapor transmission with respect to common Korean paper, and the paper containing Mandarin peels 1 and 2, Lemon peel 3 and Dekopon peels 1 and 2 had a slightly lower vapor transmission with respect to common Korean paper. Since all of the citrus peel paper was high in terms of vapor transmission, it was judged that they are adequate to be used as a wall paper or window paper.

As shown in FIG. 2, when the paper manufactured according to Examples 1 to 12 was analyzed with an image analyzer, the citrus peel paper was more yellowish and/or reddish than common Korean paper. In addition, due to citrus peels distributed between fibers, less inter-fiber pores were found in the paper according to Examples 1 to 12 than in common Korean paper.

In view of the aforementioned results, the citrus peel paper of the invention have excellent physical properties such as tensile strength, tear strength, bursting strength, folding endurance, vapor transmission and preservability, which are close to those of common Korean paper. 

1. A paper comprising 20 to 60 weight parts of citrus peel fiber and 100 weight parts of paper mulberry fiber.
 2. The paper according to claim 1, wherein the citrus peel fiber is prepared by cooking citrus peels in a sodium hydroxide solution to remove cellulose oil therefrom, cleaning the cooked citrus peels, and beating the cleaned citrus peels together with water in a beater.
 3. The paper according to claim 1 or 2, wherein the citrus peel fiber is a peel fiber of one selected from the group consisting of mandarin orange, lemon, orange, Kiyomi and Dekopon. 